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Long Range Order (long + range_order)

Distribution by Scientific Domains
Physics and Astronomy75%

Selected Abstracts

Silver Nanoparticles with Controlled Dispersity and Their Assembly into Superstructures

ADVANCED ENGINEERING MATERIALS, Issue 5 2010
Karsten Moh
In this paper we report on the influence of particle size distribution, particle substrate interaction, and drying behavior on the self-assembly process using ligand stabilized silver particles. Two-dimensional particle arrays were characterized using transmission electron microscopy and extensive image analysis. The formation of such structures was observed in situ using an environmental scanning electron microscope in WET-STEM mode. The results confirm that a small particle size distribution is crucial for the formation of regular particle patterns with long range order, but also the particle substrate interaction and the particle density have an influence on the degree of ordering. Additionally, we find that separated binary particle assemblies keep the orientation of their two-dimensional hexagonal lattices over alternating domains of small and big particles. This is probably enabled due to the formation of dislocations and a small change of the course of the lattice lines within the respective boundary. [source]

Optical properties of thick metal nanohole arrays fabricated by electron-beam and nanosphere lithography

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 5 2009
Ahmad Reza Hajiaboli
Abstract Optically thick metallic nanohole structures were fabricated using two different methods , electron-beam and nanosphere lithography. The nanosphere lithography technique was based on self-assembling of polystyrene or silica nanospheres (0.560,1.25 ,m in diameter) followed by the deposition of a silver film. The holes size and periodicity of the patterns as well as optical properties (transmission and reflection in the Visible,NIR) of the structures were investigated. The extraordinary optical transmission (EOT) was studied experimentally in both structures and it was found to be dependent on the geometrical parameters (holes shape, diameter and periodicity of structures). As the samples were made for long range order, the effect of the defects like missing holes, change of periodicity or variation of the holes shape, were also studied. The experimental results, especially the position of the SPR band in the different nanohole structures, were compared with those found by simulation carried out with 3D FDTD (finite difference time domain). (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]

Single crystalline 2D porous arrays obtained by self organization in n-InP

PHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2003
S. Langa
Abstract Self organization is a rather common phenomenon during pore formation in III,V semiconductors. The so called tetrahedron-like pores, the domains of crystallographically oriented pores in n-GaAs, or the macroscopic voltage oscillations in n-InP at high constant current densities are examples of a self organization process. In this paper we will discuss two-dimensional arrays of pores in n-InP with the unique property that they may form a single crystal as a result of a self organization process. The reasons for this long range order and its dependence on the etching conditions will be discussed. [source]

Dynamical T-matrix theory for high-density excitons in coupled quantum wells

PHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 10 2006
R. Zimmermann
Abstract Excitons in coupled quantum wells open the possibility to reach high densities close to equilibrium. In a recent experiment employing a lateral trap potential, a blue shift and a broadening of the exciton emission line has been seen [D. W. Snoke et al., Solid State Commun. 134, 37 (2005)]. The standard Hartree,Fock treatment can explain the blue shift but fails to give a finite broadening. Starting from the (spin-dependent) many-exciton Hamiltonian with direct and exchange potential, we present a dynamical T-matrix calculation for the single-exciton Green's function which is directly related to the frequency- and angle-resolved photoluminescence. The calculated spectrum is blue shifted and broadened due to exciton,exciton scattering. At high excitation, both the spectrum and the angular emission are getting narrow. This is a direct manifestation for off-diagonal long range order and a precursor of condensation. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source]